The importance of measurements for eye and jitter

Author: Dennis Lennie

Published 1st November 2009


‘If it hasn’t got eye and jitter measurements, it’s about as useful as a chocolate teapot’ recalled Paul Nicholls, PHABRIX sales and marketing manager.
‘This was one comment made by a prominent broadcast engineer that stuck with me when we began to research the critical toolset required on the new eye and jitter PHABRIX SxE’.
Having taken this to heart, PHABRIX made automated measurements for eye and jitter parameters a prominent feature in the development of its new PHABRIX SxE which began shipping in volume just prior to IBC2009.

This laboratory accurate new hand held instrument benefits from a physical layer eye and jitter toolset combined with the generation and analysis features of its highly successful sibling, the PHABRIX SxA. Both support 3G-SDI, HD-SDI and SD-SDI as standard across the feature-set along with AES in/out and 16 channels of embedded audio – quite a punch for a single portable unit.
Applications for the SxE can be found across a whole range of broadcast activities from studios, transmission stations and large broadcast installations through to broadcast equipment manufacturers R&D, test, and support departments.

Areas of use include commissioning, fault finding and confidence testing within the broadcast chain. OB operators in particular will appreciate the compact nature of the instrument enabling them to test in confined areas where signal integrity is essential.

All physical layer measurements are automatic and displayed simultaneously on the Eye display. This screen provides the engineer with a quick go/no-go indication that the signal meets the relevant SMPTE physical layer specifications for SDI. Measurements include eye amplitude, rise time, fall time, rise/fall difference, rising edge overshoot, falling edge overshoot, alignment/timing jitter and approximate cable length. These automatic, accurate measurements can be logged against alarm parameters for extended periods of time with the results available in a log file for later reference.
An additional Jitter display provides experienced engineers with the tools required to help understand the nature of any eye modulation or jitter present. These include amplitude and timing histograms, decade filters (10 Hz, 100 Hz, 1 KHz, 10 KHz and 100 KHz), cursors and eye acquisition control.

Finding the source of jitter in a system is where the PHABRIX SxE excels using hardware and software algorithms usually associated with very expensive bench-bound equipment. Timing and amplitude histogram displays provide the user with useful statistical information and are the engine behind the automatic measurement system.

Having won several prestigious awards at IBC this year for the SxE, UK based company PHABRIX picked up a successive IABM award to add to last years’ prestigious Peter Wayne IABM award for design and innovation. Selling at a fraction of the cost of equivalent performance instruments the SxE is a ray of light in these times of economic gloom.

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